Field of the Invention
The present invention relates to a method for manufacturing a single crystal diamond.
Description of the Related Art
Diamond has a wide band gap of 5.47 eV and has extremely high dielectric breakdown electric field strength of 10 MV/cm. Further, as diamond has the highest thermal conductivity among materials, if used in an electronic device, it is possible to advantageously realize a high-power electronic device.
Further, diamond which has high drift mobility can be the most advantageously used as a high speed electronic device among semiconductors in terms of Johnson performance index. Diamond is thus said to be an ultimate semiconductor suitable for use in high frequency and high power electronic devices.
Currently, most of single crystal diamond for producing a diamond semiconductor is diamond referred to as Ib type diamond which is synthesized using a high-pressure method. This Ib type diamond contains a number of nitrogen impurities and can be manufactured in a size of only approximately 5 mm square, and therefore has less practicability.
In contrast, a CVD (Chemical Vapor Deposition) method can provide large-area poly crystal diamond having a diameter of approximately 6 inches with high purity. However, it is difficult to produce single crystal diamond which is generally suitable for use in electronic devices because conventionally, a single crystal Si substrate is used as a base substrate, which makes it extremely difficult to cause heteroepitaxial growth due to a great difference in a lattice constant between the substrate and the diamond (a degree of lattice mismatching of 52.6%).
Therefore, various studies have been conducted, and it has been reported that a method is effective in which a Pt (see Non-Patent Document 1) or Ir (see Non-Patent Document 2) film is formed on a base substrate as a foundation film and a film of diamond is formed thereon.
Currently, studies of an Ir film have been particularly proceeding, and in this method, the Ir film is heteroepitaxially grown on the base substrate such as MgO and Si. Further, it has been proposed to put a buffer layer between the Ir film and the base substrate as necessary. Still further, a method in which diamond is grown after ion irradiation pretreatment is performed by a DC plasma CVD method using hydrogen-diluted methane gas, enables manufacturing of diamond, which had initially been submicron-size diamond, but, currently, enables manufacturing of diamond with a size of several millimeters.